UFC's Felice Herrig Gets In Vegas Street Fight Over A Penny

UFC fighter Felice Herrig is giving TMZ Sports a blow-by-blow of her bloody Vegas street fight ... and she tells us the whole thing started over a penny.

35-year-old Herrig --the #12 ranked strawweight -- was in Sin City for UFC 246 ... when her night out on the town started to resemble her day job.

Herrig was walking with a friend between two casinos when a woman halted foot traffic to retrieve the cent.

“I was just like, ‘Dude it’s just a penny,’” Herrig told us. “And then I thought it was over and I was walking out with my friend, Kim, and she comes up from behind me and she was like, ‘It was on heads!’”

The penny-pincher declined Herrig’s request to get out of her face.

“So, I kind of shoulder bumped her to kind of let her know to go away, and she came at me,” Herrig tells us. “She punched me in the nose. I just remember punching her two times back.”

Herrig wasn't seriously hurt ... but did have her nose busted. Luckily for the woman who allegedly started beef with Felice ... she wasn't badly hurt either.

“I wanted to double-leg her, but I’m still recovering from my ACL injury,” Herrig tells us.

Felice says she doesn’t go out in public looking for fights, but she had a message for anyone else looking to start with her.